Storm slamming parts of Ontario with snow will bring rainy, mild weather to the Maritimes

Rainy conditions are pictured along the Dartmouth, N.S., waterfront on July 8, 2025. (Carl Pomeroy/CTV Atlantic)

A strengthening storm out of the U.S. midwest will bring a snowfall heavy enough to create hazardous travel conditions for parts of Ontario on Wednesday. The same storm system will bring rainy and milder conditions to the Maritimes. Temperatures will turn colder again as we approach the start of December.

Winter storm warning

A large portion of Ontario, from the northern shoreline of Lake Superior to the border with western Quebec, is under a winter storm warning issued by Environment Canada. The warning encompasses communities such as Thunder Bay, Timmins, Kapuskasing, and Moosonee. Snow totals of 20 to 60 cm are possible Tuesday night through Thursday.

The snow is expected to be accompanied by periods of wind gusts as high as 70 km/h from the north. Extensive blowing snow is expected and the weather agency is advising whiteout conditions are likely. The combination of heavy snow and poor visibility could result in road closures.

Parts of the Trans-Canada Highway are expected to be impacted by the adverse weather conditions. That includes sections that run close to the Lake Superior shoreline and the northern branch that runs from Nipigon to Matheson.

Rainy and mild for the Maritimes

Far to the east of the centre of the storm, the Maritimes will end up on the milder, rainy side of the storm.

Rain will arrive in southwestern New Brunswick and southwestern Nova Scotia early Wednesday morning. Rain will develop across the Maritimes by Wednesday mid-afternoon. There may initially be some wet snow in northern areas of New Brunswick.

Further rain, drizzle, and fog can be expected Wednesday night into early Thursday morning. Rain totals will generally range from 10-to-30 mm. Northern areas of New Brunswick are likely to finish lower with total precipitation amounts of 5-to-10 mm.

South and southwest winds will bump temperatures up in the Maritimes Wednesday and Thursday. High temperatures on Wednesday will be in the high-single digits and low teens, but cooler in northern New Brunswick. Similar high temperatures are expected on Thursday.

Chilling out before December

After the milder conditions Wednesday and Thursday, temperatures will turn cool and then chilly on Friday and the weekend.

Temperatures on Friday will be seasonably chilly. That includes daytime highs in the low-to-mid single digits.

A northwest wind on Saturday will tap into some colder air out of Quebec and high temperatures will range from a few degrees below to just a few degrees above freezing. Similar temperatures are expected for Sunday.

We may get a taste of some colder December conditions next week, from Wednesday onward. A weakening polar vortex (semi-permanent circulation of very cold air over the Arctic) is expected to send some bitterly cold air into northern Quebec. If we get into a northwest wind, that could push some of that cold down into parts of the Maritimes.